Phase rotator



Sept. 4, 1956 D. M. KALTENBACHER PHASE ROTATOR Filed Oct. 30, 1952 FIG. I

OUTPUT OUTPUT FIG. 2

DOMINIC M. KALTENBACHER INVENTOR.

United States Patent PHASE ROTATOR Dominic M. Kaltenbacher, Baltimore, Md., assignor to Bendix Aviation Corporation, Towson, Md., a corporation of Delaware Application October 30, 1952, Serial No. 317,791

12 Claims. (Cl. 323-119) This invention relates to phase shifting devices and more particularly to a device for shifting the phase of an alternating current over substantially a 360 range.

It is an object of this invention to provide a phase shifting device in which a phase shift of substantially 360 can be obtained by the use of a single control shaft.

It is another object of the invention to provide such a device which is simple and inexpensive.

These and other objects and advantages of the invention are realized by an arrangement in which a pair of serially connected resistors is connected between the anode and cathode of an amplifier tube, one of the resistors being a potentiometer, and the cathode being connected to the slider of the potentiometer. The extremities of the potentiometer are connected together and to an output terminal. The input to the amplifier is switched between opposite phases as the slider passes thru its center position, the switching of the input and operation of the slider being controlled by a single shaft.

In the drawing:

Fig. 1 is a schematic diagram of a circuit embodying the invention;

Fig. 2 is a view in perspective of a control shaft having mounted on it the potentiometer and switch of Fig. 1; and,

Fig. 3 is a schematic diagram of a modification to the circuit of Fig. 1.

The circuit of Fig. 1 comprises a triode 1, having a cathode resistor 2 and a plate resistor 3 of equal values. The plate is also connected to a series circuit consisting of a resistor 4, a condenser 5, and a potentiometer 6. The extremities of the potentiometer 6 are connected together and to an output terminal and the slider is connected to the cathode of the triode 1.

The input to the triode is applied to the primary winding of a transformer 7, the secondary of which is centertapped to ground. The input may either be balanced or unbalanced to ground. The terminals of the secondary form the fixed contacts of a single-pole, double-throw switch 8. The movable contact of this switch is connected to the control grid of the triode 1, by way of a potentiometer 9.

The movable contact of the switch 8 and the slider of the potentiometer 6 are ganged to a single control shaft indicated by the dashed line 10. The switch 8 is arranged to be operated as the slider of the potentiometer 6 passes through its center position.

By virtue of its equal cathode and plate resistors the triode 1 operates as a phase splitter with the voltages at the plate and the cathode being equal and 180 apart in phase. When the resistance of the potentiometer 6 is at aminimum, the output of the system is taken from the cathode of the triode 1 which is in phase with the voltage on the grid. The resistor 4 lessens the shunting effect of the plate circuit. When the resistance of the potentiometer 6 is at a maximum, the output of the system is taken from the plate of the triode 1 which is 180 out of phase "ice with the grid voltage. Since the resistance of the potentiometer 6 does not become infinite and the resistor 4 has a finite resistance, the maximum phase shift is less than However, the potentiometer 6 will produce any degree of phase shift over its range of adjustment, the limits being set by the reactances in the series network.

Since the extremities of the potentiometer 6 are connected together and constitute one terminal of the co trol, the other being the slider, maximum resistance will occur at the center of rotation and resistance will be at a minimum at both extremes of the slider travel. The resistance taper is symmetrical and the resistance variation will thus be duplicated on both sides of the central position of the slider. Since the switch 8 is operated at the center of travel of the slider, it is possible to select any degree of phase shift in substantially 360 in the mechanical range of the potentiometer.

There is shown in Fig. 2 a control shaft arrangement for a circuit such as that shown at Fig. 1. The shaft 10 has mounted upon one end the slider 11 of a potentiometer 6, which is shown by way of example as an annular wire wound type of potentiometer surrounding the shaft 10. Mounted on the same shaft 19 is a cam 12, onehalf of the periphery of which is formed with one radius, the other half being formed of a different radius. One of the junction points on the periphery of the cam between the two portions of different radii occurs at the same angular position of the shaft as does the mid-point of the slider travels about the potentiometer 6. The earn actuates a micro-switch 8, the switch being internally spring biased to one position when opposite the portion of the cam having the lesser radius and being urged to its alternative position by the portion of the cam having the larger radius.

There is shown in Fig. 3 an alternative arrangement for the potentiometer 6 of Fig. 1. In this arrangement the condenser 5 is tapped to the center of the potentiometer, the two ends of the latter being free. The taper of the potentiometer is linear. In this form of the invention maximum resistance occurs at the two ends of the potentiometer and minimum resistance at its mid-point. This form of potentiometer is less preferable because it requires a center-tap and adjustment is critical in the vicinity of switch actuation.

If desired, the switch 8 may be a part of the potentiometer assembly and be actuated by the slider at the midpoint of its travel, rather than by the cam as shown. A toggle switch mounted at the mid-point of the potentiometer and, positioned to be actuated by the slider would provide satisfactory results.

What is claimed is:

I l. A phase rotating system comprising a resistor, a contacting element movable along said resistor, an output terminal for said system, means connecting said system to said resistor in symmetry with respect to the midpoint of said resistor, means applying an alternating voltage to said contacting element, means applying an alternating voltage of identical frequency and amplitude but of opposite phase to said connecting means, means moving said contacting element along said resistor and means reversing the phase of said applied voltages when said contacting element passes the mid-point of said resistor.

2. A phase rotating system comprising a resistor, means connecting the terminals of said resistor to each other, a contacting element movable along said resistor, means applying an alternating voltage to said contacting element, means applying an alternating voltage of identical frequency and amplitude but of opposite phase to said terminals, an output terminal for said system conductively connected to said terminals, means moving said contacting element along said resistor and means reversing the id applied voltages when said contacting elee mid-point of said resistor.

system comprising a resistor, 21 cl ment movable along said resistor, means .2 mid point of said resistor to said system, means applying an alternating voltage to said contacting element, means applyinn an alternating voltage of identical and amplitude but of opposite phase to ilequency said connecting means, an output terminal for said sysn conductively connected to said mid-point, means moving said contacting element along said resistor and means reversing the phase of said applied voltage as said contacting element passes the mid-point of said resistor.

4. A phase rotating system comprising an amplifier having at one point an output in phase with the input thereto and at a second point an output in phase opposition with said input, a resistor, 21 contacting element movable along said resistor, means conductively connectone of said points to said resistor in symmetry with the mid-point thereof, means conductively connecting the second of said points to said contacting element, an output terminal for said system conductively connected to the junction of said one of said points and said resistor, means applying alternating voltage to the input of said amplifier, means moving said contacting element and a reversing the phase of the alternating voltage apo sai input as said contacting element passes the min-point of said resistor.

5. A phase rotating system comprising an amplifier having at one point an output in phase with the input thereto and at a second point an output in phase opposition with said input, resistor, a contacting element movable along said resistor, means conductively connec ng one or" said points to both terminals of said resistor, an output terminal for said system at said connectiug means, means conductively connecting the secend or said oints to said contacting element, means applying an alternating voltage to the input of said amplifier, means moving said contacting element, and means reversing the phase of the alternating voltage applied to said input as said contacting element passes the mid-point of said resistor.

6. A phase rotating system comprising an amplifier having at one point an output in phase with the input thereto and at a second point an output in phase opposition with said input, a resistor, 21 contacting element movable along said resistor, means conductively connecting one of said points to the mid-point of said resistor, an output terminal for said system at said connecting means, means conductively connecting the sec- 0nd of said points to said contacting element, means applying alternating voltage to the input of said amplifier, means moving said contacting element, and means reversing the phase of the alternating voltage applied to said input as said contacting element passes the midpoint of said resistor.

7. A phase rotating system comprising an amplifier having at one point an output in phase with the input thereto and at second point an output in phase opposition with said input, a pair of serially connected resistors conductively connected between said points, the first of said resistors being connected to the second in symmetry with respect to the mid-point of said second to sistor, said second resistor being connected to one of said points by means comprising a contacting element movable along said second resistor, means moving said contacting element, an output terminal for said system at the junction of said resistors, means applying an alternatvoltage to the input of said amplifier and means reversing the phase of the alternating voltage applied to said input as said contacting element passes the mid-point of said second resistor.

8. A phase rotating system comprising an amplifier having at one point an output in phase with the input thereto and at a second point an output in phase opposition with said input, a pair of serially connected resistors conductively connected between said points, the first of said resistors being connected to both terminals of the second, said second resistor being connected to one of said points by means including a contacting element movable along said second resistor, means mom t; said contacting element, an output terminal for said system at the junction of said resistors, means applying an alternating voltage to the input of said amplifier, and means reversing the phase of said alternating voltage as applied to said input as said contacting element passes the mid-point of said second resistor.

9. A phase rotating system comprising an amplifier having at one point an output vin phase with the input thereto and at a second point an output in phase opposition with said input, a pair of serially connected rcsistors conductively connected between said poi the first of said resistors being connected to the mid oint of the second, said second resistor being connected to one of said points by means including a contacting element movable along said second resistor, means moving said contacting element, an output terminal for said system at the junction of said resistors, means applying an alternating voltage to the input of said amplifier and means reversing the phase of said alternating voltage as applied to said input as said contacting element pa: es the mid-point of said second resistor.

10. A phase rotating system comprising an amplifier having at one point an output in phase with input thereto and at a second point an output in phase oppos' 'on with said input, a pair of serially connected resistors cor tively connected between said points, the first of sail resistors being connected to the second in symmetry with respect to the mid-point of said second resistor, said second resistor being connected to one of said points by means comprising a contacting element movable along said second resistor, an output terminal for system at the junction of said resistors, means applying an alternating voltage to the input of said amplifier, a switch for reversing the phase of said alternating voltage as plied to said input and a control shaft controlling the o eration of said switch and the movement of said contacting element, said control shaft operating said switch as said contacting element passes the mid-point of said second resistor.

11. A phase rotating system comprising an amplifier having at one point an output in phase with the input thereto and at a second point an output in ph' e opposition with said input, a pair of serially connected resistors conductively connected between said points, the first of said resistors being connected to both terminals oi the second, said second resistor being connected to one of said points by means comprising a contacting element movable along said second resistor, an output terminal for said system at the junction of said resistors, means applying an alternating voltage to the input of said amplifier, a switch for reversing the pnase or" said alternating voltage as applied to said input, and a control shaft controlling the operation of said switch and the movement of said contacting element, said control shaft operating said switch as said contacting element passes the mid-point of said second resistor.

12. A phase rotating system comprising an amplifier having at one point an output in phase with the input thereto and at a second point an output in phase opposition with said input, a pair of serially connected resistors conductively connected between said points, the first of said resistors being connected to the mid-point of the second, said second resistor being connected to one of said points by means comprising a contacting element movable along said second resistor, an output terminal for said system at the junction of said resistors, means applying an alternating voltage to the input of said amplifier, a switch for reversing the phase of said alternating volt- 5 6 age as applied to said input and a control shaft con- References Cited in the file of this patent trolling the operation of said switch and the movement UNITED STATES PATENTS of said contacting element, said control shaft operating said switch as said contacting element passes the mid- 2,228,843 Palmer 1941 point of said second resistor. 5 FOREIGN PATENTS 620,222 Great Britain Mar. 22, 1949 

